Dealing with ground loop hum in a stereo / 2 amp setup

Discussion in 'Effects, Pedals, Strings & Things' started by Kenny Blue, Apr 17, 2016.

  1. Kenny Blue

    Kenny Blue Silver Supporting Member

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    I am wanting to use a second amp to create a wet / dry, 2 amp set up but am dealing with the accompanying ground loop hum. I have done a search and read various threads about this, and I understand that there are a number of ways of doing a wet/dry set up and also of dealing with ground loop hum. But I wanted to just discuss it a bit here with anyone who has some experience doing it.

    One reason that I have now begun wanting to do this again is that I just watched a recent episode of "That Pedal Show" (a really enjoyable You Tube show by the way) that deals with doing a 2 amp setup. Dan explained several ways of using Stereo effects with 2 amps and the one he likes the best used the effects in front of the amp, then split to two different amps.

    The way he does it is to route the signal through the pedals on his pedal board to a splitter/ hum eliminator (specifically he is using a device from GigRig called a HumDinger). He then takes one of the split signals, from the HumDinger, on through the time based effects (chorus, delay and reverb) to the "wet" amp and the other split signal, from the HumDinger, to a "dry" amp.

    I would like to do the same or a similar thing. I might instead use my FX loop in my "wet amp" for the delay and reverb, and then send the second split signal to a second ("dry") amp.

    I have checked out that device that Dan is using (the GigRig HumDinger) and it can be ordered from Analogman or from the GigRig website but it is kind of pricey compared with other choices. Ebtech also has a splitter/hum eliminator box called a Hum Eliminator, which is about 1/2 the price of the GigRig box.

    But Ebtech also makes something called the Hum X with is even less expensive and it simply is a small device that you plug one of the two amps into (the power cord plug) and then plug that into the power outlet. This stops the ground loop hum where the power comes into the second amp.

    I understand that the more expensive unit (GigRig) also addresses the problem of signal degradation from long audio cords on stage, in addition to eliminating ground loop hum. But basically right now I am just playing at home and do not need to deal with long cables or various stage applications.

    So I am wondering.... To just solve the ground loop hum problem in doing a two amp set up, is using the simple Ebtech Hum X device (which seems to be the most simple and inexpensive choice) to stop the ground loop hum at the power cable of one of the amps totally sufficient? Or is there some other desirable benefit to getting one of the splitter/hum eliminator boxes (from Ebtech or GigRig or somewhere else) to add to my pedal board to run the signal through going to the amps ?

    And I do not need a splitter box specifically to create a split signal because I will just use one of my stereo pedals at the end of my pedal board signal chain to split the signal to the two amps (and as I said above I will probably also put my delay and reverb in the FX loop of my one of the two amps).

    Anyone use any of these devices or have any experience with, understanding of or advice about using them... and specifically about the Ebtech Hum X product ?
     
    Last edited: Apr 17, 2016
  2. WhiskeyTango

    WhiskeyTango Member

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    I've used the Hum X before, and it did work just fine. It eventually walked off on it's own, never to be seen again.

    You'll probably get 10 replies saying this, but PLEASE don't use the 2-3 dollar 2-prong adapters to lift the ground on one of the amps. Those make YOU the ground. If the amp in question where to short to chassis, YOU'D be the path to ground. Not good at all.

    If you have a DI box with a ground lift, you could use this on one of the amp inputs just to make sure you're chasing the right problem. Impedance would likely be off, but you could still test for hum removal.

    I'm an at-home player myself, and use a similar setup to connect to both an amp, and to my PC via USB. I get a horrible, horrible hum through the amp as soon as the computer (USB) side is connected. I'm running the amp's input through a DI (for the ground lift) to resolve. I don't get much hum when I try two amps in stereo, but I've tried the DI there too, and it still helped. The same solution would likely work for you too.

    Ideally, I'd have something like the Radial TwinCity, but for home use, my 20 dollar solution (used DI) worked just fine for me. I'm cheap, so I was looking for the cheapest, decent path to a handy ground lift option for me, and this was it.

    My two typical home configs to use this:
    Guitar>DI, DI Lo-Z>amp, DI Hi-Z through to computer
    -or-
    Guitar>cheap ABY, output A>DI, DI Low-Z>amp1, Output B>amp2
     
    Last edited: Apr 17, 2016
  3. manasquanto

    manasquanto Member

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    I use the Ebtech hum eliminator box and keep it on the pedalboard. I found them used for around $40.

    One side of the stereo signal gets a patch cable through one channel, the other side goes straight to the other amp.

    The nice thing about this little box is that I have a spare isolated output to run direct or to a third amp if I want.
     
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  4. Kenny Blue

    Kenny Blue Silver Supporting Member

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    Yes... thanks. I do understand the danger of actually lifting the ground from one amp. I won't be doing that.
     
  5. AceBSpankin

    AceBSpankin Prince of Ales

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    Lehle P-Split
    Fixes grounding and phasing issues!!
    Built like a brick.
     
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  6. justnick

    justnick Gold Supporting Member

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    The Ebtech is a good solution and in most cases seems to resolve the issue. There can be other sources of information he ground loop on your board but I'd still start by using the hum-x to lift the ground on one amp.
     
  7. CaptainAwesome

    CaptainAwesome Member

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    The Hum-X worked perfectly when I had a ground loop issue. I'd start there given the price and simplicity of the solution.
     
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  8. Kenny Blue

    Kenny Blue Silver Supporting Member

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    Thanks for your help guys ! I think I will try either the Ebtech Hum X or the Hum Eliminator . I have seen both of these used for fairly low, comparable prices.
     
  9. direneed

    direneed Member

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    The Diamond ST-Mix is my favorite device for this. I've tried the Ebtech devices before (10 yrs ago maybe) and noticed a pretty serious signal loss. Can't beat the price of the Ebtech, though. I picked up a Radial Switchbone and used that for a while before stumbling across the ST-Mix, which I got in a package deal on a Memory Lane. Diamond shows them as discontinued but they told me a couple of years ago that they were considering another run of them. I bought both of mine used for dirt cheap.
     
  10. jawajt

    jawajt Member

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    The way I avoid the hum with using two amps, is by plugging them into the same outlet. I know that's not always a possibility, depending how far apart they are.
     
  11. Kenny Blue

    Kenny Blue Silver Supporting Member

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    A bit of a thread ressurection...

    I spoke with someone from Ebtech in the last couple of weeks and he just recommended the Hum X device for what I was wanting to do. The Hum X is just a little thing that you plug into an outlet / powerstrip and then plug the powercord of one of the two amps into it. It's simple, relatively inexpensive and is not messing with the guitar signal path at all.

    But one thing that devices like the Switchbone does, in addition to dealing with ground loop hum is also offering a switch that deals with phase switching.

    I do not really know what that is. And obviously the Hum X does nothing in regards to the two amps being in Phase or out of Phase with each other.

    So if I plug out of a stereo pedal at the end of my pedal signal chain into two amps, other than dealing with ground loop hum, am I going to need the ability to switch or correct the phase as well ?
     
  12. DaveKS

    DaveKS Member

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    Totally depends on the amps, every time a signal goes through a triode of a tube or some solid state circuits it inverts phase, but most amps use both sides of a 12ax7 for instance which is a dual triode tube so by time it goes through both triodes it's back to phase it started with. But some amp designs have been known to only use 1/2 of a dual triode. Some pedals may flip phase, if one of those is after your Y split it can throw your amps out of phase. Way to many variables to know if there will be a phase problem unless your intimately familiar with your whole signal chain, but when it happens you'll know it, the 2 speaker cancel each other out and your left with this thin sounding shadow of what your sound should sound like.
     
  13. tubetonez

    tubetonez Member

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    When one speaker cone moves forward, the out-of-phase cone moves backward. This cancels out a lot of bottom end. Some vintage Fenders are out of phase with vintage Marshalls, I know this was the case with the BFDR and Marshall 50w Lead I owned. Also, aside from the preamp/amp circuitry some brands of speakers are/were out of phase with others. JBL's were notorious for being opposite polarity than most others.
     
  14. erksin

    erksin Member

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    Been running a stereo rig for over twenty years - always just used a ground lift adapter and have never ever had a safety issue doing so. I plug both amps and the pedalboard into the same surge protection power strip.

     
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  15. Kenny Blue

    Kenny Blue Silver Supporting Member

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    So then... for example at home, if both amps and all the pedals in the signal chain are plugged into the same powerstrip (then of course plugged into one outlet) it is safe (?) to use one of those ground lift adapters on one of the two amps to eliminate ground loop hum ?
     
  16. erksin

    erksin Member

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    Like I said, twenty years with no safety issues. No zaps, no noise, no problems.
     
  17. Kenny Blue

    Kenny Blue Silver Supporting Member

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    Cool... thank you for your input.
     
  18. Jacob Van Noy

    Jacob Van Noy Member

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    I can't comment on the safety being absolute but I've been doing the same thing as erksin for 10 years live, rehearsal, and in the studio. Plug both amps and pedalboard into a nice surge protected power strip and use a ground lift adaptor on one amp. I figure I have the pedalboard grounded and one amp (not to mention the power strip) and I've never once had a problem.
     
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  19. erksin

    erksin Member

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    Right - as long as the wall receptacle your rig is plugged into has ground, you are good to go. I keep one of those continuity testers plugged into my outlet strip too so I can check it wherever I go.
     
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  20. tech21nyc

    tech21nyc Member

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    I often run two rigs and have the Ebtech Hum eliminator which works very well but... It will really be beneficial to have a phase switch so you can easily find out if there is a phase issue. You also have to keep in mind if you are running both amps that certain effects can and do flip the phase when engaged. As long as you're using the same effects to both amps this shouldn't be a problem. I have also used various ABY boxes and the Lehle Dual SGoS works very well. Tone Bone makes a unit called the Twin City and the Bigshot ABY. If you aren't going to be switching back and forth a passive box can work. If you have the iso transformer engaged you need to have a buffer between your passive guitar pickup and the iso transformer or you will get a loss of tone. The Lehle is the only unit I know of that has a custom wound transformer that will not load down a passive pickup.
     

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